An idle idea of Darwin’s has turned, over the years, into a rather controversial psychological test. A seemingly random list of animals “pass” this test, but some recent results call into question what a passing result means. And it's all what what you see when you look in a mirror.

If you pass a mirror and happen to see an unbecoming smudge on your face, you would brush it off, right? Congratulations, you have just passed a simple test of self-awareness. Maybe. The mirror test started off with a stray thought of Darwin’s; he recorded the antics of an orangutan in a zoo playing with a mirror he had given it, and wondered what exactly the ape made of the image of itself. Did it recognize itself in the mirror? And if so, what would that recognition mean?

Gordon Gallup wondered the same thing in 1970, and so he devised a test to see if animals were capable of self-recognition. First he got chimpanzees accustomed to mirrors, monitoring their progress from aggressive displays to playfulness and curiosity. Then he knocked the chimps out and put a spot of odorless dye on one of their eyebrows. The revived chimpanzees were again shown their image in the mirror. Gallup watched to see if they motioned to the dot on their own bodies – which most chimps did. Any animal that could understand that the image in the mirror was a reflection of itself showed self-awareness, Gallup reasoned. Chimps, then, were aware of themselves as separate from their surroundings.

Over time, the list of self-aware animals grew. Dolphins, European magpies, orcas, all the great apes, and eventually elephants, have passed the test. Monkeys have not. Humans, generally, pass the test, but it takes them a while. Babies begin to pass at around 18 months, and almost no humans have failed the test past the age of 24 months.

...or so we thought. Although a study done in 1986 showed that even kids brought up in cultures without mirrors went for the dot, most studies have been conducted in America and Europe. Recent studies done in Fiji and Kenya show that some 6-year-olds don’t pass what Gallup considered to be the mirror test. These children seem unconcerned with the dot, and were uncomfortable with the test as a whole. Although they did indicate through motions that they knew that the mirror was reflecting their own image, they mostly froze when they looked at the reflection. In one study, only two out of 82 children passed the test.

No one could argue that a 6-year-old child lacks self-awareness, so the question is, what is the test actually testing? If it’s not self-awareness we’re measuring, then what could American and European babies have in common with magpies that they don’t have in common with other babies the same age? And what do Kenyan infants share with Fijian babies that they don't share with Americans?

It’s possible that kids who don’t respond to the dot test look at the reflection in the mirror as a third thing, not technically themselves and not technically other. While test-passing babies are like chimpanzees and orcas, non-passing babies could also have their own cohorts in nature. Some studies show that, although capuchin monkeys fail the dot test, they are aware of their reflections in the mirror as different from both themselves and different from other monkeys. They’re not wrong. Children who look at a mirror and freeze, ignoring the dot, might be going with the philosophy of Magritte and thinking, “Ceci n’est pas une bébé.”

Then again, these toddlers might not be getting quite so abstract. Children who pass the dot test and children who fail might differ in something as technically simple as a concern about a dot on their face. The mirror test presumes that the most important thing you think about when seeing your reflection is an unfamiliar dot, and the most sensible thing to do is fix it immediately, or at least investigate it. For some time, people didn’t think that gorillas had self-awareness based on this assumption. It was only when they observed gorilla behavior after the test that they realized that the gorillas were hiding away before they attempted to wipe away the dots in private – meaning gorillas had not only self-awareness but a sense of social embarrassment. In 2004, the time of the Kenyan and Fijian mirror studies, elephants had not passed the test, either. In 2006 researchers got one out of three Asian elephants to pass the test. They attributed the change in results to their experiment offering the elephants a big mirror that the animals were able to touch, rather than a small mirror that they could not reach or investigate. As for the elephants who failed, the researchers believe that an animal that coats itself in mud isn't necessarily going to care about a small mark on its face. Recent studies show that macaque monkeys do not touch the dot on their heads, but do use them study hard-to-see areas of their own bodies, like their genitals.

The test, it seems, has more variables than we might think. It clearly has a wider range of results than previously indicated. So the self-awareness test might be more a test of priorities - priorities picked up so early that they surface even in babies.